Casio CZ/ VZ/ FZ - Pro Series

--- In CZsynth@yahoogroups.com, "steve_the_composer" <smw-mail@...> wrote:
>
> Never mind--neither the gear nor the manuals list the patents covering the instruments. (It couldn't have been that easy, I guess.)
> Steve

Casio seems to enshroud the inner working of their instruments as much as possible.

The case bottom of my Casio SA-41 e.g. lists the US patents 4121284, 4371923 and 4942516, those however only refer to third party inventions about very generic principles of small microcomputers (key debouncing, multitasking, integrated I/O etc.). I guess this was rather done as a warning that the product is patented while not telling competitors where to search for the important parts.

Unlike Yamaha, Casio is generally infamous for secrecy about the inner working of even their oldest and most outdated keyboard ICs; perhaps driven by fear of patent lawsuits they had lost several times, they never published datasheets nor sold individual sound ICs (only complete instrument designs) to 3rd party manufacturers. Another plausible reason may be, that to be the first in competition, Casio apparently often released products based on new inventions *before* they had finished patenting them. Thus service manuals typically don't explain more about Casio special ICs than barely necessary to identify a faulty one. At least IC pin names in schematics stay complete, although unused ones often lack description.

Otherwise some Casio patent texts even describe complete instruments nicely detailedly. E.g. the PT-50 with ROM-Pack algorithm is described in US patents 4624171 and (later) 33607. The VL-Tone 1 is detailedly explained in US patent 4475429. Yamaha instead patented every tiny technical detail separately (e.g. the PlayCard system concept is split among a variety of US patents, including 4413545, 5144875, 4466324, 4454797, 4387620, 4587878, 4406203), which makes it much harder to conclude the inner working of a certain instrument.


With TM synthesis I suspect that it might be a hidden secret inside the Casio HT-6000 (which sounds noticeably different than other SD-synths), but this also may be result of all those separate VCFs. I likely will need to check the unfiltered waveforms by oscilloscope. Seeing backfoldet peaks of sine waves (like in the patent) would be the best indication for Triangular Wave Modulation. Also the PT-100/MT-88 single chip CPU may use it, but I haven't checked the waveforms either.